The AVAPS dropsonde system has been used for hurricane research since the late 1990s (Hock and Franklin 1999; Halverson et al.
The 8-9 September 2011 flight sampled an atmospheric river event and was designed to intercompare temperature and humidity profiles from AVAPS, HAMSR, and S-HIS.
Wick, G., 2015: Hurricane and Severe Storm Sentinel (HS3) Global Hawk AVAPS Dropsonde System.
(5) Comparisons between S-HIS and AVAPS suggest a dry bias in the AVAPS data above 400 hPa, so relative humidities with respect to ice above about 8 km should be closer to saturation within the cloud system.
The National Center for Atmospheric Research (NCAR) GPS dropsonde system called the Airborne Vertical Atmospheric Profiling System (AVAPS) was developed in the 1990s and is the only operational dropsonde system in the world capable of providing research-quality, high-resolution, reliable atmospheric profiles in hard-to-reach locations.
The NOAA/Aircraft Operations Center (AOC) runs the AVAPS program for NOAA.
However, the 3D position was computed using precise drop location from the AVAPS aircraft data system and integrating the velocity to obtain position with each individual measurement from the dropsonde.